Zinc complexes of amine mono(phenolate) [NOO2] ligands: Controlling coordination modes by bulk of phenolate substituents

Article abstract of DOI:10.1002/ejic.200600019

The coordination chemistry of three tripodal monoanionic amine mono(phenolate) ligands bearing two methoxy sidearm donors with ethylzinc(II) is reported. Reacting diethyl-zinc with the ligand precursor bearing bulky (tBu) phenolate substituents led cleanl

Full text of DOI:10.1002/ejic.200600019

FULL PAPER
DOI: 10.1002/ejic.200600019
Zinc Complexes of Amine Mono(phenolate) [NOO2] Ligands: Controlling
Coordination Modes by Bulk of Phenolate Substituents
Stanislav Groysman,[a] Ekaterina Sergeeva,[a] Israel Goldberg,[a] and Moshe Kol*[a]
Keywords: Zinc / N,O ligands / Tripodal ligands / Polynuclear complexes
The coordination chemistry of three tripodal monoanionic
amine mono(phenolate) ligands bearing two methoxy side-
arm donors with ethylzinc(II) is reported. Reacting diethyl-
zinc with the ligand precursor bearing bulky (tBu) phenolate
substituents led cleanly to a mono(ethyl) mononuclear Cs-
symmetric zinc complex according to spectroscopic data. X-
whereas the other one was weakly bound. The ligand pre-
cursors bearing less bulky electron-donating (Me) or elec-
tron-withdrawing (Br) phenolate substituents led cleanly to
dinuclear pentacoordinate complexes, bridged by phenolate
oxygens, in which only one of the two sidearm donors was
bound, and in a weak manner.
ray structure analysis revealed a semi-pentacoordinate com- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
plex as one of the methoxy sidearm donors was tightly bound
Germany, 2006)
glycinate ([NON2]),[8] and 2-mercaptobenzyl-bis(2-pyridyl-
methyl)amine ([NN2S]) ligands (Figure 1).
Introduction
[9]
Zinc plays a major role in bioinorganic chemistry, fulfill-
ing structural and catalytic functions in various enzymes.[1,2]
When coordinated by S-based (cysteinate) ligands, or by a
mixed set of S- and N-based (histidine) ligands, the role of
zinc is mainly structural.[2] On the other hand, a coordina-
tion sphere containing O-based ligands is characteristic for
a catalytic metal site, as the O-based hard donors (H2O or
HO–) are readily replaced at the zinc metal center, providing
a vacant coordination site to be occupied by a substrate.[2]
According to these general observations, simple analogues
of the zinc biological active sites are sought.
In such research, controlling the nuclearity of metal spe-
cies is a major goal. For many applications, mononuclear
species are desired, as they lead to better-defined catalytic
performance in comparison to multinuclear species. The
most practical route toward such species is the utilization
of chelating multidentate ligands such as the “tripodal” li-
gands, having three donor arms, which have become very
abundant in the last two decades.[3] One particular family
of tripodal ligand, that attracts ever-increasing attention, is
the family of tripodal ligands possessing a central nitrogen
donor atom, in addition to the three donor arms. Several
ligand families of this type have been employed in zinc
chemistry, including neutral tris(picolyl)amine ([NN3]),[4,5]
N-bis[2-(methylthio)ethyl]-N-[(6-neopentylamino-2-pyridyl)-
methyl]amine ([NS2N]),[6] and tris[(N-tert-butylcarbamoyl)-
methyl]amine ([NN3]) ligands,[7] or monoanionic dipicolyl-
Figure 1. Various tripodal ligands, having a central nitrogen donor
employed in zinc chemistry.
The zinc chemistry of monoanionic amine mono(phenol-
ate) ligands, carrying two additional arms, has been investi-
gated in the last decade, mainly by the groups of Fenton
and Vahrenkamp.[10–13] The advantages of the amine mono-
(phenolate) ligands include their straightforward synthesis,
and their broad structural diversity.[10–17] Yet, until now, the
zinc chemistry of these ligands was limited to ligands hav-
ing two additional pyridine arms,[10–12] or pyridyl and pyr-
rolidinyl arms (Figure 2).[13] The [NONpy2] ligands, having
no substituents, or tBu substituents at the phenolate ring,
were shown to bind the metal firmly through all four do-
nors, with the three “tripodal” donors lying in the equato-
rial plane.[11,12] Both ligands led to neutral mononuclear
complexes, possessing an additional, monodentate ligand in
[a] School of Chemistry, Raymond and Beverly Sackler Faculty of
Exact Sciences, Tel Aviv University,
Tel Aviv 69978, Israel
E-mail: moshekol@post.tau.ac.il
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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S. Groysman, E. Sergeeva, I. Goldberg, M. Kol
FULL PAPER
the fifth position: Cl, Br, I, OPh, and SPh. In this study, we benzyl (ArCH2N) protons at δ = 3.31 ppm (these groups are
were aiming at extending the chemistry of tripodal reflected by a mirror plane). The NCH2CH2OMe protons
monoanionic [NOX2] ligands. Specifically, we wanted to re- appear as four distinct signals, of ddd (or dt) multiplicity,
1
veal structural effects on coordination chemistry of whose connectivity pattern was validated by a 2D JC,H
[NOO2]-zinc complexes, in which zinc binds to labile oxygen (HMQC) experiment. This indicates that all four methylene
donors.
protons of a particular “sidearm” are different; thus, the
ligand seems to wrap around the metal in a well-defined
fashion, in which the two sidearms are reflected by a mirror
plane. However, the possibility of a fast (on the NMR time-
scale) exchange process, in which only one of the sidearms
is bound at a given time, cannot be excluded a priori.
To distinguish between these two possibilities, we carried
out a VT NMR experiment for 1 in [D8]toluene. For the
latter scenario, two different sidearms should be observed
at low temperatures. In contrast, for the compound contain-
ing an effective mirror plane, no significant difference be-
tween proton spectra at room temp. vs. low temperatures
should be anticipated. Upon cooling to as low as 210 K, no
splitting in the peak attributed to the OCH3 groups was
observed; the NCH2CH2OMe appeared as four distinct sig-
nals as well, though all signals were somewhat broadened.
The signals attributed to the ethyl group also underwent
no change. This data is consistent with a Cs-symmetrical
complex in solution, featuring binding of both sidearms
(Figure 3). The slight broadening of peaks is attributed to a
low-barrier conformational flip of the methylene-phenolate
group. A freezing of this flip would result in a C1-symmetri-
cal complex, as revealed from the X-ray structure of 1. The
X-ray structure also reveals different MeO–Zn bond lengths
(vide infra).
Figure 2. Two tripodal amine mono(phenolate) ligands, employed
in zinc chemistry.
Results and Discussion
We previously reported the preparation of the ligand pre-
cursor Lig1H.[17] Lig2H and Lig3H ligand precursors were
prepared in a similar way, via a single-step Mannich con-
densation between the respective phenol, secondary amine,
and formaldehyde (Scheme 1). The ligand precursors were
obtained as yellow oils, and their identity was confirmed by
NMR and elemental analyses.
The complex of the nonbulky [NOO2] electron-donating
ligand Lig2 was prepared in a similar way, by a protonolysis
reaction between the ligand precursor Lig2H and Et2Zn
(Figure 3). Complex 2 was obtained as colorless crystals
upon recrystallization from ether. Even at room temp. the
NMR spectrum of 2 in deuteriobenzene displays different
features: the methylene NCH2CH2OMe protons appear as
two broad signals vs. four sharp signals of ddd (dt) multi-
plicity for 1 (Figure 3). The OCH3 protons appear as a sin-
gle resonance at δ = 2.85 ppm at room temp. and the ethyl
group gives rise to single triplet and quartet resonances, at
δ = 0.39 and 1.56 ppm, respectively. However, in contrast
to 1, cooling 2 to 210 K causes splitting of the OCH3 reso-
Scheme 1. Synthesis of ligand precursors Lig1H–Lig3H.
Diethylzinc provides a convenient entry into zinc chemis- nance into two discrete signals (coalescence at 221 K). The
try with sufficiently acidic ligands.[18,19] An ethereal solu- quartet signal attributed to the metal-bound methylene was
tion of Lig1H was added to a hexane solution of diethylzinc split into two multiplets at that temperature as well, signify-
at –30 °C, followed by warming to room temperature and ing a different chemical environment for the two methylene
stirring for 1 h. Subsequent removal of solvent and protons. Thus, a different binding of the nonbulky [NOO2]
recrystallization from pentane led to pure 1 in 80% yield, ligand to the metal should be anticipated, according to the
obtained as colorless crystals. According to its NMR spec- VT-NMR spectroscopic data (Figure 3).
tra, 1 contains a single type of phenolate ring, and a single
The X-ray structure determination of these complexes
type of metal-bound ethyl group. As anticipated, the zinc- provided a solid evidence for the different coordination
bound methylene group gives rise to high-field NMR sig- modes of these [NOO2] ligands around zinc. According to
nals [δ(13C) –1.8 ppm; δ(1H) 0.58 ppm]. The 1H and 13C our expectations for the structure of 1, the ligand is bound
NMR spectra of this compound clearly signify a Cs-sym- to the metal through all four donors, forming a mononu-
1
metrical species at room temp. Thus, the H spectrum fea- clear, pentacoordinate species of highly distorted TBP ge-
tured a single resonance for the OCH3 groups at δ = ometry (Figure 4, Table 1). In the previously disclosed zinc
2.85 ppm [δ(13C) 58.7 ppm], and a sharp singlet for the two complexes featuring the [NO(Npy)2] ligand,[11,12] the three
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Zinc Complexes of Amine Mono(phenolate) [NOO2] Ligands
FULL PAPER
1
Figure 3. Syntheses of the amine mono(phenolate) complexes 1 and 2, and their proposed structures; (bottom), based on VT H NMR
spectra (top). See text for details.
arms of the tripodal ligand occupied the equatorial posi-
tions, while the central amine and the additional mono-
dentate ligand were located in the axial positions. In the
present case, the phenolate oxygen, the central nitrogen,
and the ethyl methylene carbon are located in the equatorial
plane, whereas the methoxy donors occupy the axial posi-
tions. The phenolate oxygen, amine donor, and the ethyl
methylene carbon all feature strong bonding to the metal
center. In contrast, the two methoxy groups are inequiva-
lent, displaying weak binding to the metal: 2.308 vs.
2.598 Å. The pronounced difference in bond lengths may
result from the conformation of the ethyl group, as its meth-
ylene carbon points toward the remote methoxy group, or
from the conformation of the phenolate ring, as the tBu
group points toward that group as well, or by a combina-
Figure 4. The X-ray structure of 1. ORTEP representation, 50%
probability.
tion of both. It may also signify an “arrested” dynamic pro-
cess equilibrating bound and unbound sidearm donors. The
Zn–O–C(Ph) angle is narrow (114.9°), as is anticipated for
a d10 metal complex experiencing no π-donation from the Zn2O2 core is a common structural motif in zinc coordina-
phenolate oxygen to the metal, vs. 128–148° in d0 or d2 tion chemistry, found frequently in zinc-phenolate spe-
(TaV, VIII, VV, or TiIV) complexes.[20–22]
cies.[23–27] The Zn–O(Ph) bond lengths are not identical, be-
In a sharp contrast to the structure of 1, 2 is a dinuclear ing 2.018 and 2.123 Å, respectively. One of the sidearms is
complex of Ci-symmetry, in which the two nearby zinc unbound, creating a pentacoordinate, nearly TBP geometry
atoms (Zn···Zn separation of 3.108 Å) are bridged by the at each metal center. One of the phenolate oxygen atoms
two phenolate oxygen atoms (Figure 5, Table 1). This and the methoxy donor are in the axial position [O(Ph)-Zn-
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S. Groysman, E. Sergeeva, I. Goldberg, M. Kol
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Table 1. Bond lengths [Å] around Zn in the solid-state structure of cant broadening in the OCH3 and Zn-CH2 resonances, no
1, 2, and 3.
splitting was observed down to 200 K, which may indicate
a lower-energy process in 3 than in 2; it does not exclude,
however, the possibility of a mononuclear, nearly Cs-sym-
metrical complex.
1
2
3
Zn1–O2
Zn1–O2Ј
Zn1–O3
Zn1–O4
Zn1–N5
Zn1–C6
1.931(2)
2.018(2)
2.123(2)
2.549(3)
2.036(5)
2.143(4)
2.451(5)
2.308(2)
2.598(2)
2.150(2)
1.962(2)
The X-ray structure analysis provided a clear evidence
for the dinuclear nature of 3 (Figure 6). In the solid state,
the Ci-symmetric 3 possesses a very similar structure to that
of 2, displaying two pentacoordinate metal centers in close
proximity (Zn···Zn separation of 3.163 Å), bridged by the
phenolate oxygen atoms. The bond lengths in 3 are reminis-
cent of those in 2; the major structural difference between
these structures lies in the Zn–O(R)Me bond lengths
[2.451(5) in 3 vs. 2.549(3) Å in 2]. The stronger bonding of
the weak donor in 3 may be traced back to the electron
deficiency at the metal center, as a result of the electron-
poor ligand.
2.169(3)
1.986(4)
2.155(6)
1.975(7)
(R)OMe 159.0°], whereas the second phenolate oxygen, the
ethyl methylene carbon, and the central nitrogen are in the
equatorial positions. Consistently with the previous struc-
ture, the central amine is bound tightly (2.169 Å), and the
methoxy donor is bound very weakly (2.549 Å).
Figure 6. The X-ray structure of 3. ORTEP representation, 40%
probability. The asymmetric unit contains only half of the Ci-sym-
metric dimer, and the second half is generated by a symmetry oper-
ation.
Figure 5. The X-ray structure of 2. ORTEP representation, 40%
probability. The asymmetric unit contains only half of the Ci-sym-
metric dimer, and the second half is generated by a symmetry oper-
ation. The structure also contains a disordered solvent molecule,
not shown here.
On the basis of the above results, we propose that a point
of divergence for the different nuclearity in [NOO2]ZnEt
An additional ligand, employed in this research, was species lies in a delicate balance between the weakness (la-
Lig3, carrying ortho, para bromo substituents, that are com- bility) of the dative Zn–O(R)Me bond and the steric bulk
parable in size to the methyl groups, yet are electron-with- imposed by the groups in the ortho positions of the phenol-
drawing and may reduce the tendency of the phenolate oxy- ate ring. Presumably, formation of a dinuclear phenolate-
gen atoms to act as bridging groups. The ligand precursor bridged species in the [NOO2] zinc complexes is favorable
Lig3H was treated with diethylzinc in analogy to Lig1H and due to the weakness of the Zn–O(R)Me dative bond. How-
Lig2H; the product 3 was obtained in a good yield after ever, the formation of dinuclear species is precluded by suf-
washing out of the impurities with pentane and ether. In ficient steric bulk at the ortho positions of the phenolate
general, the room temp. H NMR spectrum of 3 displays group.[28] As a result, mononuclear species arise, in which
1
similar features to that of 2. In both cases, the NCH2CH2O the weak, yet nonbulky, second O(R)Me donor is able to
methylene protons give rise to two resonances: For 2, these bind to the metal center, accomplishing a pentacoordinate
are represented by two broad peaks; for 3, one of these geometry.
signals is broad, while the second appears as a relatively
To summarize, we investigated the coordination chemis-
sharp triplet. The VT NMR behavior of 3 was not identical try of zinc(II) in the environment of the amine mono(phen-
to the spectrum of 2: for example, the methylene olate) ligands, carrying two neutral oxygen-type arms, in
NCH2CH2O protons were observed in 2 at 278 K as four addition to the anionic phenolate oxygen. A neutral oxygen
broad multiplets, while in 3 they gave rise to two broad donor, known to bind weakly to zinc, was found to display
signals at that temperature. Moreover, in spite of a signifi- varying coordination modes, influenced by the steric bulk
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Zinc Complexes of Amine Mono(phenolate) [NOO2] Ligands
FULL PAPER
www.ccdc.cam.ac.uk/data_request/cif. Elemental analyses were per-
formed in the microanalytical laboratory in the Hebrew University
of Jerusalem.
at the phenolate ring. In the case of small groups at the
phenolate ring, formation of a dinuclear complex was ob-
served, in which every metal atom was bound to two phe-
nolate oxygen atoms, at the expense of binding of a second
weak donor. In contrast, utilization of bulkier, tBu, groups
Synthesis of Lig2H: 2,4-Dimethylphenol (5.5 mL, 46 mmol), bis(2-
methoxyethyl)amine (13 mL, 89 mmol), and formaldehyde (13 mL,
at the phenolate ring prohibited the formation of a dinu- 37% in water) were mixed in MeOH (20 mL). The mixture was
heated to 110 °C in a pressure flask and stirred for 48 h, yielding a
deep orange biphasic solution. The crude reaction mixture was
poured into water/CH2Cl2 (40 mL each), the organic phase was
separated, dried with anhydrous MgSO4, and the solvent was re-
moved under reduced pressure. The traces of amine were removed
under vacuum (0.5 mbar), while heating to 80 °C, yielding the de-
sired product as orange oil (9.243 g, 35 mmol, 76%). C15H25NO3
(267.36): calcd. C 67.38, H 9.42, N 5.24; found C 67.31, H 9.71, N
clear complex, leading to a mononuclear species instead, in
which both neutral oxygen donors were bound.
Experimental Section
General: All manipulations of the metal complexes were performed
under dry nitrogen in a nitrogen-filled glovebox. 2,4-Di-tert-bu-
tylphenol, bis(2-methoxyethyl)amine, formaldehyde (37% in
water), and diethylzinc (1.0  in hexane) were obtained from Ald-
rich and used without purification. Lig1H was prepared as de-
scribed previously.[17] Ether was purified by reflux and distillation
under dry Ar from Na/benzophenone. Pentane was washed with
HNO3/H2SO4 prior to distillation from Na/benzophenone. [D6]-
Benzene was flushed with Ar and stored on molecular sieves in the
glovebox. [D8]Toluene was dried on Na before being used. NMR
spectroscopic data for the metal complexes were collected with
Bruker AC-200 and AC-400 spectrometers, and referenced to pro-
tio impurities in [D6]benzene and [D8]toluene (δ = 7.15 and
2.1 ppm, respectively) and to the 13C chemical shift of benzene (δ
= 128.06 ppm). Routine characterization of metal complexes con-
sisted of 1H, BB, and DEPT-135 13C NMR experiments, performed
in [D6]benzene at 298(2) K. VT NMR experiments were performed
in [D8]toluene. X-ray diffraction measurements were performed
with a Nonius Kappa CCD diffractometer system, using Mo-Kα (λ
= 0.7107 Å) radiation. The analyzed crystals were embedded within
a drop of viscous oil and freeze-cooled to 110 K. The structures
were solved by a combination of direct methods and Fourier tech-
niques using SIR-92 software,[29] and were refined by full-matrix
least-squares with SHELXL-97.[30] The crystal and experimental
data are summarized in Table 2. CCDC-294424 (for 1), -294425
(for 2), and -294426 (for 3) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
1
5.44. H NMR (200 MHz, CDCl3): δ = 10.32 (s, 2 H, O-H), 6.74
(br. s, 2 H, Ar-H), 6.52 (br. s, 2 H, Ar-H), 3.69 (s, 2 H, ArCH2N),
3
3.43 (t, JH,H = 5.5 Hz, 4 H, NCH2CH2O), 3.23 (s, 6 H, OCH3),
3
2.70 (t, JH,H = 5.5 Hz, 4 H, NCH2CH2O), 2.11 (s, 6 H, Ar-
CH3) ppm. 13C NMR (50.29 MHz, CDCl3): δ = 153.7 (CO), 130.6
(CH), 127.6 (C), 126.9 (CH), 124.8 (C), 121.5 (C), 70.5 (CH2), 58.8
(OCH3), 58.6 (CH2), 53.4 (CH2), 20.5 (CH3), 15.8 (CH3) ppm.
Synthesis of Lig3H: 2,4-Dibromophenol (1.97 g, 7.8 mmol), bis(2-
methoxyethyl)amine (2 mL, 13.6 mmol), and formaldehyde
(3.2 mL, 37% solution in water) were mixed in MeOH (20 mL).
The mixture was stirred and refluxed for two weeks. The crude
reaction mixture was poured into water/CH2Cl2 (20 mL each), the
organic phase was separated, dried with anhydrous MgSO4, and
the solvent was removed under reduced pressure. The remaining
product was dried (0.5 mbar, 100 °C) for 2 h, yielding the desired
product as brown oil (2.86 g, 7.2 mmol, 92%). 1H NMR (200 MHz,
4
4
C6D6): δ = 7.57 (d, JH,H = 2.4 Hz, 2 H, Ar-H), 6.79 (d, JH,H
=
2.4 Hz, 2 H, Ar-H), 3.23 (s, 2 H, ArCH2N), 3.01 (t, 3JH,H = 5.1 Hz,
3
4 H, NCH2CH2O), 2.94 (s, 6 H, OCH3), 2.34 (t, JH,H = 5.4 Hz, 4
H, NCH2CH2O) ppm. 13C NMR (100.58 MHz, CDCl3, 300 K): δ
= 154.4 (CO), 134.1 (CH), 130.4 (CH), 125.3 (C), 111.1 (C), 110.5
(C), 70.4 (CH2), 59.2 (OCH3), 58.4 (CH2), 53.6 (CH2) ppm.
Synthesis of 1: Lig1H (86 mg, 0.25 mmol) was dissolved in ether
(1 mL) and cooled to –35 °C. While cold, it was added slowly to a
pre-cooled solution of ZnEt2 in hexane (1.0 , 0.25 mL). The re-
sulting bright yellow solution was warmed to room temp. and
stirred for 1 h. The solvent was removed under reduced pressure,
the resulting bright yellow solid was dissolved in pentane and the
solution was left at –35 °C overnight. Colorless crystals of X-ray
quality were separated from the solution, washed with cold pentane
and dried under reduced pressure to afford 1 (91 mg, 0.20 mmol,
80%). C23H41NO3Zn (444.97): calcd. C 62.08, H 9.29, N 3.15;
found: C 61.85, H 9.31, N 3.25. 1H NMR (400 MHz, C6D6, 298 K):
Table 2. Crystallographic experimental details.
1
2
3
Formula
fw
a [Å]
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
C23H41NO3Zn C17H29NO3Zn C15H23Br2NO3Zn
444.94
360.78
26.8350(7)
26.8350(7)
10.6420(3)
90.00
90.00
90.00
tetragonal
I41/a
490.53
10.4670(5)
9.2700(6)
18.1480(10)
90.00
93.036(4)
90.00
monoclinic
P21/c
9.4730(6)
9.8160(6)
13.890(1)
82.162(4)
69.988(3)
81.258(4)
triclinic
4
4
δ = 7.58 (d, JH,H = 2.7 Hz, 2 H, Ar-H), 6.88 (d, JH,H = 2.7 Hz,
2 H, Ar-H), 3.31 (s, 2 H, PhCH2N), 2.96 (ddd, 2JH,H = 10.1, JH,H
= 9.0, JH,H = 3.7 Hz, 2 H, NCH2CH2O), 2.85 (s, 6 H, OCH3),
3
3
2
3
2.81 (dt, JH,H = 10.1, JH,H = 4.5 Hz, 2 H, NCH2CH2O), 2.41
(ddd, 2JH,H = 13.3, 3JH,H = 8.9, 3JH,H = 4.5 Hz, 2 H, NCH2CH2O),
Crystal system
Space group
V [Å3]
2
3
2.17 (dt, JH,H = 13.3, JH,H = 4.0 Hz, 2 H, NCH2CH2O), 1.86 [s,
9 H, C(CH3)3], 1.63 (t, JH,H = 8.1 Hz, 3 H, Zn-CH2CH3), 1.46 [s,
9 H, C(CH3)3], 0.59 (q, JH,H = 8.1 Hz, 2 H, Zn-CH2CH3) ppm.
¯
P1
3
1194.55(14)
1.237
1.049
2
7663.5(4)
1.251
1.293
1758.41(17)
1.853
5.952
3
Dc [g cm–1
]
13C NMR (100.58 MHz, C6D6, 298 K): δ = 164.4 (CO), 138.5 (C),
135.1 (C), 125.3 (CH), 124.1 (CH), 122.4 (C), 68.5 (CH2), 59.6
(CH2), 58.7 (OCH3), 56.5 (CH2), 35.9 [C(CH3)3], 34.2 [C(CH3)3],
32.4 [C(CH3)3], 30.2 [C(CH3)3], 13.5 (Zn-CH2CH3), –1.8 (Zn-
CH2CH3) ppm. 1H NMR (400 MHz, C7D8, 301 K, selected reso-
µ [cm–1
]
Z
16
4
No. of measd. reflns.
5559
4543
3226
No. of reflns. [I Ͼ 2σ(I)] 3890
3307
2205
R1 [I Ͼ 2σ(I)]
wR2 [I Ͼ 2σ(I)]
GOF
0.0524
0.1104
1.003
0.0534
0.1498
1.042
0.0546
0.1163
1.010
3
nances): δ = 3.30 (s, 2 H, PhCH2N), 3.01 (ddd, 2JH,H = 10.0, JH,H
3
= 9.0, JH,H = 3.7 Hz, 2 H, NCH2CH2O), 2.90 (s, 6 H, OCH3),
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S. Groysman, E. Sergeeva, I. Goldberg, M. Kol
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2.81 (dt, 2JH,H = 10.1, 3JH,H = 4.5 Hz, 2 H, NCH2CH2O), 2.45 2.41
(CH2), 58.5 (OCH3), 57.9 (CH2), 56.1 (CH2), 13.4 (Zn-CH2CH3),
–1.8 (Zn-CH2CH3) ppm.
(ddd, 2JH,H = 13.4, 3JH,H = 9.0, 3JH,H = 4.5 Hz, 2 H, NCH2CH2O),
2
3
2.21 (dt, JH,H = 13.4, JH,H = 4.2 Hz, 2 H, NCH2CH2O), 1.56 (t,
Supporting Information (see footnote on the first page of this arti-
cle) includes VT NMR spectra for complexes 1–3.
3JH,H = 8.1 Hz, 3 H, Zn-CH2CH3), 0.49 (q, JH,H = 8.1 Hz, 2 H,
3
Zn-CH2CH3) ppm. 1H NMR (400 MHz, C7D8, 210 K, selected res-
onances): δ = ca. 3.1 (br. s, 2 H, PhCH2N), 2.89 (br. s, 2 H,
NCH2CH2O), 2.84 (s, 6 H, OCH3), 2.60 (br. s, 2 H, NCH2CH2O),
2.29 (br. s, 2 H, NCH2CH2O), 1.87 (br. s, 2 H, NCH2CH2O), 1.76
Acknowledgments
3
3
(t, JH,H = 8.0 Hz, 3 H, Zn-CH2CH3), 0.69 (q, JH,H = 8.1 Hz, 2
H, Zn-CH2CH3) ppm.
We thank the Israel Science Foundation and the United States-
Israel Binational Science Foundation for financial support. We
thank Adi Yeori for helpful discussions.
Synthesis of 2: Lig2H (165 mg, 0.62 mmol) was dissolved in ether
(2 mL), cooled to –35 °C, and added slowly to a pre-cooled solu-
tion of ZnEt2 in hexane (1.0 , 0.63 mL). The resulting bright yel-
low solution was warmed to room temp. and stirred for 1 h. The
solvent was removed under reduced pressure, the resulting bright
yellow solid was dissolved in diethyl ether (ca. 3 mL overall) and
the solution was left at –35 °C for 2 days. Colorless crystals of X-
ray quality were separated from the solution, washed with cold
ether and dried under reduced pressure to afford 2 (157 mg,
0.44 mmol, 71%). C34H58N2O6Zn2 (721.61): calcd. C 56.59, H 8.10,
[1] G. Parkin, Chem. Rev. 2004, 104, 699.
[2] S. J. Lippard, J. M. Berg, Principles of Bioinorganic Chemistry,
University Science Books, Mill Valley, CA, 1994, p. 354.
[3] G. Parkin, Chem. Commun. 2000, 1971.
[4] N. N. Murthy, K. D. Karlin, J. Chem. Soc., Chem. Commun.
1993, 1236.
[5] H. Adams, N. A. Bailey, D. E. Fenton, Q.-Y. He, J. Chem. Soc.,
Dalton Trans. 1997, 1533.
[6] L. M. Berreau, R. A. Allred, M. M. Makowska-Grzyska,
A. M. Arif, Chem. Commun. 2000, 1423.
[7] M. Ray, B. S. Hammes, G. P. A. Yap, A. L. Rheingold, A. S.
Borovik, Inorg. Chem. 1998, 37, 1527.
[8] A. Abufarag, H. Vahrenkamp, Inorg. Chem. 1995, 34, 2207.
[9] R. Burth, A. Stange, M. Schäfer, H. Vahrenkamp, Eur. J. Inorg.
Chem. 1998, 1759.
[10] H. Adams, N. A. Bailey, D. E. Fenton, Q.-Y. He, J. Chem. Soc.,
Dalton Trans. 1996, 2857.
[11] A. Trösch, H. Vahrenkamp, Eur. J. Inorg. Chem. 1998, 827.
[12] A. Trösch, H. Vahrenkamp, Inorg. Chem. 2001, 40, 2305.
[13] A. Abufarag, H. Vahrenkamp, Inorg. Chem. 1995, 34, 3279.
[14] H. Adams, N. A. Bailey, C. O. Rodriguez de Bazan, D. E. Fen-
ton, Q.-Y. He, J. Chem. Soc., Dalton Trans. 1996, 2233.
[15] Y. Inoue, K. Matyjaszewski, Macromolecules 2003, 36, 7432.
[16] Y. Inoue, K. Matyjaszewski, Macromolecules 2004, 37, 4014.
[17] S. Groysman, E. Sergeeva, I. Goldberg, M. Kol, Inorg. Chem.
2005, 44, 8188.
[18] C. K. Williams, L. E. Breyfogle, S. K. Choi, W. Nam, V. G.
Young Jr, M. A. Hillmyer, W. B. Tolman, J. Am. Chem. Soc.
2003, 125, 11350.
[19] M. H. Chisholm, C.-C. Lin, J. C. Gallucci, B.-T. Ko, Dalton
Trans. 2003, 406.
[20] S. Groysman, I. Goldberg, M. Kol, E. Genizi, Z. Goldschmidt,
Organometallics 2004, 23, 1880.
[21] S. Groysman, I. Goldberg, Z. Goldschmidt, M. Kol, Inorg.
Chem. 2005, 44, 5073.
[22] S. Groysman, E. Tshuva, I. Goldberg, M. Kol, Z. Goldsch-
midt, M. Shuster, Organometallics 2004, 23, 5291.
[23] E. Bukhaltsev, I. Goldberg, A. Vigalok, Organometallics 2005,
24, 5732.
1
N 3.88; found C 56.27, H 8.25, 3.86. H NMR (400 MHz, C6D6,
4
4
300 K): δ = 7.05 (d, JH,H = 1.9 Hz, 2 H, Ar-H), 6.66 (d, JH,H
=
2.1 Hz, 2 H, Ar-H), 3.83 (s, 2 H, PhCH2N), 3.13 (br. s, 4 H,
NCH2CH2O), 2.86 (s, 6 H, OCH3), 2.85 (br. s, 4 H, NCH2CH2O),
3
2.51 (s, 3 H, Ar-CH3), 2.29 (s, 3 H, Ar-CH3), 1.11 (t, JH,H
=
3
8.1 Hz, 3 H, Zn-CH2CH3), 0.40 (q, JH,H = 8.1 Hz, 2 H, Zn-
CH2CH3) ppm. 1H NMR (400 MHz, C7D8, 301 K, selected reso-
nances): δ = 3.65 (s, 2 H, PhCH2N), 3.07 (br. s, 4 H, NCH2CH2O),
2.90 (s, 6 H, OCH3), 2.61 (br. s, 4 H, NCH2CH2O), 2.47 (s, 3 H,
3
Ar-CH3), 2.29 (s, 3 H, Ar-CH3), 1.51 (t, JH,H = 8.1 Hz, 3 H, Zn-
CH2CH3), 0.38 (q, JH,H = 8.1 Hz, 2 H, Zn-CH2CH3) ppm. 1H
3
NMR (400 MHz, C7D8, 210 K, selected resonances): δ = 2.85 (s, 3
3
H, OCH3), 2.77 (s, 3 H, OCH3), 1.79 (t, JH,H = 8.0 Hz, 3 H, Zn-
CH2CH3), 0.40 (br. s, 1 H, Zn-CHHCH3), 0.31(br. s, 1 H, Zn-
CHHCH3) ppm. 13C NMR (100.58 MHz, C6D6, 300 K): δ = 161.4
(CO), 132.4 (CH), 129.5 (CH), 128.4 (C), 124.1 (C), 123.4 (C), 68.9
(CH2), 59.3 (CH2), 58.4 (OCH3), 53.2 (CH2), 20.8 (Ar-CH3), 17.8
(Ar-CH3), 13.7 (Zn-CH2CH3), –1.7 (Zn-CH2CH3) ppm.
Synthesis of 3: Lig3H (51 mg, 0.13 mmol) was dissolved in an ether/
THF mixture (5 mL) and added to a solution of ZnEt2 in hexane
(1.0 , 0.13 mL). The resulting dark yellow solution was stirred for
1.5 h. The solvent was removed under reduced pressure, and the
resulting yellow solid was washed with pentane (ca. 2 mL) and
ether (2 mL) and dried under reduced pressure to afford 3 (47 mg,
74%). X-ray quality crystals were obtained upon recrystallization
from ether. C30H46Br4N2O6Zn2 (981.09): calcd. C 66.07, H 10.52,
N 7.97; found C 66.11, H 10.77, N 7.88. 1H NMR (400 MHz,
4
C6D6, 300 K): δ = 7.82 (d, JH,H = 2.6 Hz, 2 H, Ar-H), 6.86 (d,
4JH,H = 2.6 Hz, 2 H, Ar-H), 3.06 (s, 2 H, PhCH2N), 2.80 (s, 6 H,
[24] K. Matsufuji, H. Shiraishi, Y. Miyasato, T. Shiga, M. Ohba, T.
3
OCH3), 2.69 (t, JH,H = 5.4 Hz, 4 H, NCH2CH2O), 2.24 (br. s, 2
¯
Yokoyama, H. Okawa, Bull. Chem. Soc. Jpn. 2005, 78, 851.
3
H, NCH2CH2O), 1.99 (br. s, 2 H, NCH2CH2O), 1.53 (t, JH,H
=
[25] J. S. Matalobos, A. M. García-Deibe, M. Fondo, D. Navarro,
M. R. Bermejo, Inorg. Chem. Commun. 2004, 7, 311.
[26] A. J. Atkins, D. Black, R. L. Finn, A. Marin-Beccera, A. J.
Blake, L. Ruiz-Ramirez, W.-S. Li, M. Schröder, Dalton Trans.
2003, 2730.
3
8.1 Hz, 3 H, Zn-CH2CH3), 0.49 (q, JH,H = 8.1 Hz, 2 H, Zn-
CH2CH3) ppm. 1H NMR (400 MHz, C7D8, 301 K, selected reso-
nances): δ = 3.10 (s, 2 H, PhCH2N), 2.85 (s, 6 H, OCH3), 2.76 (t,
3JH,H
=
5.4 Hz,
4
H, NCH2CH2O), ca. 2.3 (br. s,
2
H,
=
[27] For a heptadentate monophenolate ligand leading to a dinu-
clear zinc complex, see: H. Sakiyama, R. Mochizuki, A. Suga-
wara, M. Sakamoto, Y. Nishida, M. Yamasaki, J. Chem. Soc.,
Dalton Trans. 1999, 997.
[28] The “heteroscorpionate” ligands studied by Carrano led to
complexes of different nuclearity depending on the presence of
a tBu group on a phenolate ring. See: T. C. Higgs, K. Spartal-
ian, C. J. O’Connor, B. F. Matzanke, C. J. Carrano, Inorg.
3
NCH2CH2O), ca. 2.1 (br. s, 2 H, NCH2CH2O), 1.48 (t, JH,H
3
8.1 Hz, 3 H, Zn-CH2CH3), 0.42 (q, JH,H = 8.1 Hz, 2 H, Zn-
CH2CH3) ppm. 1H NMR (400 MHz, C7D8, 200 K, selected reso-
nances): δ = around 2.8 (broad and flat resonance, 14 H), 2.26 (br.
3
s, 2 H), 1.78 (t, JH,H = 8.0 Hz, 3 H, Zn-CH2CH3), ca. 0.45 (br. s,
2 H, Zn-CH2CH3) ppm. 13C NMR (50.29 MHz, C6D6, 298 K): δ
= 135.6 (CH), 132.1 (CH), 128.4 (C), 126.2 (C), 117.1 (C), 67.9
2744
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 2739–2745

Zinc Complexes of Amine Mono(phenolate) [NOO2] Ligands
FULL PAPER
Chem. 1998, 37, 2263; B. S. Hammes, C. J. Carrano, Inorg. [30] G. M. Sheldrick, SHELX-97, University of Göttingen, Ger-
Chem. 1999, 38, 4593.
many, 1998.
[29] A. Altomare, M. C. Burla, M. Camalli, M. Cascarano, C. Gia-
covazzo, A. Guarliardi, G. Polidori, J. Appl. Crystallogr. 1994,
27, 435.
Received: January 10, 2006
Published Online: May 24, 2006
Eur. J. Inorg. Chem. 2006, 2739–2745
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2745